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Why Don't Meal Replacement Shakes Fill Me Up | Australia

by Hamza Jamal |

Meal replacement shakes provide the same nutritional profile as a balanced, wholesome meal in convenient shake form, the idea being to substitute for a meal when you're tight on time or watching your calorie intake.

The best shakes keep you full for 3-4 hours, although a fast metabolism and a calorie deficit when dieting can make you hungry after only an hour or so.


When you dramatically reduce your calorie intake below your body's standard requirements, it can trigger some biological responses that increase appetite and hunger signals:

Metabolic adaptation

Your body's metabolism will gradually slow down on a very low-calorie diet to conserve energy and avoid using too much of your body's reserves [1].

Increased hunger hormones

Diets providing fewer than 1,000-1,200 calories can cause an increase in the hunger hormone ghrelin while decreasing levels of leptin, the hormone that signals satiety [2].

Depleted glycogen stores

Highly restrictive diets deplete the body's glycogen (stored carbohydrate) levels in the liver and muscles, increasing hunger and appetite, especially for carb/sugar-rich foods [3].

Meal replacement shakes help reset these biological triggers for a few hours, but a calorie deficit reduces their effectiveness.

Inferior Ingredients

Why Don't Meal Replacement Shakes Fill Me Up | Australia

Not all meal replacement shakes are equal in nutritional value and satiety. Many use lower-quality protein sources like whey protein concentrate or caseinates, which are inferior to whey isolates, micellar casein, and plant-based proteins.

They may also lack fibre content, relying more heavily on simple carb sources that digest quickly and fail to elicit feelings of fullness.

Shakes made with quality whole food ingredients like oats, chia, and flaxseeds - such as vybey Complete Meal Powder and Huel - are more satiating.

Fats are another key component. Dietary fats are the most calorie-dense macronutrient and promote satiety through increased cholecystokinin (CCK) production.

However, not all fats are good for fullness and satiety - you want a meal replacement shake with a healthy ratio of unsaturated fats because these increase satiety [4].

Look for these quality characteristics in your meal replacement shake.

Insufficient calories

It's also possible your meal replacement shake doesn't contain enough calories to keep you satisfied for a long time.

While calorie needs vary based on factors like age, gender, and activity level, most adults require a minimum of 300-400 calories to achieve a proper "meal" level of satiety.

If your shake only provides 150-200 calories, you're having a snack that might initially take the edge off your hunger but nothing else.

A fast metabolism

Sometimes, a legitimately filling, nutrient-dense meal replacement shake might still leave you craving more food shortly after.

If this happens to you, it could be a sign that you have a relatively fast metabolism.

A fast metabolism means you might need to increase your portion size to stay full or add some additional ingredients to your shake.

Peanut and almond butter are brilliant for adding calories and healthy fats, or you can add berries or bananas for natural sugars.  

Remember - those with a faster metabolic rate tend to digest and absorb nutrients more rapidly, so the feelings of fullness from a meal replacement can be more fleeting.

This isn't necessarily bad if your goal is to maintain your weight, but it can make dieting more challenging.

Fending off hunger when dieting

If you're trying to lose weight with meal replacement shakes, periods of hunger between shakes or meals are practically inevitable. However, there are a few strategies that can help minimise excessive hunger:

Time it right

Don't wait until you're already ravenous for your next shake or meal - that's a recipe for overeating. Instead, have your meal replacement or nutritious snack at the first signs of true hunger, like a rumbling stomach or light-headedness.

Stay busy

Boredom and inactivity tend to amplify feelings of hunger or create a false sense of hunger and cravings for sugary treats galore.

After having your meal replacement shake, take your mind off food by tackling productive tasks, walking, or staying busy with hobbies and interests.

Keep hydrated

Have a glass of water and wait 20 minutes to see if your hunger goes away – if it does, you've just saved yourself from a pointless snack.

Keep a fresh bottle of water in your bag, car, and on your desk work, and add electrolytes to your water in hot, humid environments for extra energy.


Caffeine can boost your energy levels with no massive calorie intake – coffee, green tea, and vybey Braincare Smart Focus are all great options.

The antioxidants in green tea – EGCG - promote fat burning and feelings of fullness when combined with caffeine's appetite-suppressing effects [5].

Braincare Smart Focus goes even further with a nootropic blend of lion's mane, chaga, cordyceps, and Reishi mushroom to enhance energy levels.

Have nutrient-dense snacks

On particularly tough days when hunger is aggressive, it can help to have some nutrient-dense snacks on hand to tide you over until your next meal.

Fresh fruits, veggies, nuts, seeds, Greek yoghurt, hard-boiled eggs, jerky, and low-sugar oat bars are all excellent options.

These snacks can take the edge off without going overboard on calories or spiking blood sugar excessively. Avoid highly processed, sugary snacks, as these tend to exacerbate hunger for many people. Put that cookie down! Now!

Go for a walk

A 10–15-minute walk after your meal replacement shake can increase your metabolic rate slightly while providing a mental break from obsessing over hunger.

Nowhere to walk? You can climb stairs instead, jog on the spot for five minutes, or throw out star jumps to get your heart racing.

Summing up

Why Don't Meal Replacement Shakes Fill Me Up | Australia

When you have a large calorie deficit, it's natural to feel hungrier regardless of the quality of your meal replacement shake.

A severe deficit requires your body to run partially on stored fat reserves, which increases hunger cues and cravings for sugary snacks.

vybey Complete Meal Powder helps keep you full for longer with natural whole-food ingredients like ground oats, flaxseed, corn, rice, coconut, and pea protein, which give your shake its fantastic nutritional profile.

Grab a vybey starter bundle to get started.


  1. Journal of Strength and Conditioning Research 
  2. National Library of Medicine
  3. National Library of Medicine
  4. Science Direct
  5. National Library of Medicine

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